How foundation settlement shows up in Huntsville homes
The usual symptoms: stair-step cracks running through brick or block mortar joints, diagonal cracks that start at the corner of a door or window, doors that stick in one season and swing freely in another, a gap opening between the slab edge and the bottom of the siding or brick, floors that slope toward one side of the house, and a chimney that has started to lean away from the wall it was built against.
The pattern matters more than any single symptom. Huntsville's climate swings between a wet winter and a dry late summer: December is the wettest month at 5.87 inches and September the driest at 3.49 inches, inside a 54.29-inch annual normal (NOAA 1991–2020 normals, Huntsville International Airport). Clay subsoils shrink in the dry stretch and swell again in winter, so cracks that open in October and close by March are following that cycle. The dated extremes: 2007 was the driest year on record at 28.65 inches, September and October 2016 brought only 0.47 and 0.77 inches, and 2020 reached 70.52 inches, Huntsville's fourth-wettest year, per the UAH Alabama Climate Report, as summarized.
Soil type sets how much a lot moves. NRCS SSURGO data lists Barfield and Decatur as Madison County's two largest soil series: Decatur, the familiar red clay, rates low to moderate for shrink-swell, Barfield rates high and the Colbert series rates very high. About 17.5 percent of Madison County acreage is in soils with a high or very high shrink-swell rating; in Limestone County the figure is about 1.3 percent.